Electromagnet.



W. D. LUTZ.

` ELECTROMAGNET.

APPLIcATwN FILED A116219. 1912.

1,132,783, Patented Mar. 23, 1915.

Smau/to@ UNITED srarnsrarnnr camion.

WILLIAM D. LUTZ, OF ALLINDALE BOROUGH, NEW

JERSEY, ASSIGNOR TO O'IIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY,A CORPORATION OF NEW JEP SEY.

ELECTROMAGN ET.

Application fusa August 1s, 1912. serial Nb. 715,704.

.adapted for use with alternating currents.

An object of the invention is to provide simple and reliable means lforovercoming or preventing residual magnetism.

My invention is herein illustrated as applied to an alternating currentmagnet es-- pecially designed to operate a brake for an elevator,although it will be understood that the invention may have a much moregenl eral application.

A serious drawback to the use of alternating current electric elevatorshas been the inability to secure a reliable and eflicient alternatingcurrent brake magnet. In order to prevent an excessive current beingconsumed in lmagnets of this type, it is necessary to provide a magneticpath of low resistance, so that the magnetic flux will be suihcient tochoke back the current. To accomplish this it is customary to arrangethe pole faces of the magnet, or the magnet and its armature so thatthey will be held in intimate contact while-the magnetis excited,thereby forminga practically continuous iron circuit for the magneticlines of force. Such a magnet is uncertain in operation and unreliableowing `to liability of the pole faces to hold together or stick onaccount of the residual magnetism after the current supply has been cutoff. The amount of'this residual magnetism varies greatly in any givenmagnet, and depends on the strength and direction of the energizingcurrent at the instant the circuit is opened. Careful tests of brakemagnet is of this type designed for elevator service have demonstratedthat in the same magnet the holding power due to residual magnetism mayvary from zero up to practically the full holding power of the magnet.In other words the force required to separate the magnet pole facesafter the current has been Specification of Letters Patent.

Patented Mar. 23, 19315.

cut olf may be nearly equal to that required to separate them whenreceiving full current. Owing to this liability of the residualmagnetism to assert itself at any time, such magnets have provedunreliable in practice. When used as brake magnets to hold the brakesoil? they have been the cause of serious accidents, by preventing thebrakes from beding applied when the current is cut off. Attempts havebeen made to overcome the above defect by interlposing a thin layer ofnon-magnetic ma'- terial between the pole faces of the magnet. Such anexpedient, however', has proved unsatisfactory as it not only increasesthe con sumption of current but weakens the magnet. and also renders itexcessively noisy.

i The fluctuating magnetism due to the current alt'ernatlons causes achattering noise at the pole faces which rapidly increases with anincrease of load on the magnet. In the present invention theseobjections are overcome by providing a permanent break or air space offixed dimensions in the magnetic circuit independent of the variable airgap between the pole faces.

In the accompanying drawings which illustrate a structure embodying myinvention, Figure l is an elevation view partly in section of anelectromagnet; Fig. 2 is an endfview of one section of the magnet; Fig.3 is a sectional view-as indicated by the scction line 3-3 on Fig. 2;and Fig. 4c is a view similarto Fig. 2 but showing a modiiication.

As shown on the drawing, the electromagnct comprises two sections A andvB relatively movable toward'and from each other. Each section is formedwith pole pieces l which extend into magnet coils 2. Fig. l shows two ofsuch coils in section. The exciting coils 2 are preferably lstationarybeing mounted in a suitable frame, and` the sections A and B aremovableto` ward and from each other. When themagnet coils are excitedthe two sections are drawn inward with the pole faces 0f the section Bin contact with the opposing,y faces of the section A. Each sectioncomprises a body portion 3 of brass or other non-mag-` netic materialaround which is placed a.

the magnet is of sufficient thickness.

laminated iron ring or sleeve 4, the projecting portions forming thepoles of the magnet. Surrounding the iron is a sleeve 5 of brass orother non-magnctiry material. A fiber washer G is interposed between theupper end of the iron core 4 and the body of the magnet.

The method of constructing and assembling the magnet is as follows: Aribbon or thin strip of soft iron the proper width to form the magnetcore l is tightly wound on the body portion 3, until the magnet core isThe outer sleeve or casing 5 is then heated and shrunk onto the magnet.Holes 7 and 8 are then bored to receive the pins 7 and 8' which securelykhold the several parts of the magnety in proper relative position.Portions of the magnet are also Vcut away to form projecting pole piecesl. ln order to prevent residual magnetism the magnet core is providedwith spaces or slots 9 which break the continuity of the magnetic ironcircuit, so thaty when the current is cut ofi' after the pole faces havebeen brought together there is no residual magnetism toresist theseparation of the magnet poles or to cause them to stick as it is i'vrally termed. The slots 9 are formed in the following manner after themagnet has been assembled z-Small holes l0 are drilled through the bodyportion 3 adjacent tothe iron core fl in order to admit the blade of a`hack saw. A slot or lrerf 9 is then cut with the hack saw through themagnet core. Each of the sections A and B is preferably provided withtwo of these kerfs 9 which. are located diametrically opposite eachother. l'vhen the magnet is assembled the sl ts 9 in one section areplaced in advance of those in the other section. n other words the fourslots are 90 apart. l,Vith this method of construction and arrangementthere is a slot 9 in each of the four magnet circuits. lf preferred aslot 9 may be provided between each pair of adjacent pole 4 faces of oneof the sections as illustra-ted in the body portion 3 in ypreferimce tothe ring- 5 in order. to guard against any material weakening of thestructure,

. Fig. shows a modified structure in which siX pole pieces are com,arised in, each section i "of the magnet, instead of four pole pieces asT39 the other figures. In this yinstance l have shown a slot 9 betweeneach two adgacent poles, so that no slots are required in the fixeddimensions, whereas in the usual conn l structions the air gap employedis only between the pole faces and varies with the relative position ofthe magnet and its armature or the movable sections of the magnet core.

An important feature of the present invention is the method ofconstruction as heretofore described whereby the laminated iron portionof the magnet may be' readily formed from sheet material and variousparts of the magnet securely fastened together with no possibility ofthe parts bei coming misplaced. ln' other words each of the sections Aand B is a solid structure,the several parts rigidly and securelyattached together so as to form practically an integral structure, whichis not materially weakened by the formation of the slots 9.

n operation the magnet coils 2 which are seV fixed in relatibn'to themembers A and B,

are energized to cause the said members tobe drawn-upward untiltheirpole faces are in Contact. `When the pole faces are thus in contact themagnet is practically noiseless. That is, the current alternations donot produce any material vibration and chattering at the pole faces.wifVhen the `magnet is deenerg-ized its members are immediatelyseparated as the air gaps 9 positively prevent any residual magnetism tooppose the action of the brake springs or other separating means.lilithout such slots to break the continuity of the iron circuit, thereis always more or less residual magnetism, the value of which varieswidely depending upon the strength anddirection of the energizingcurrent at the instant the circuit is broken. If an air gap or break inthe magnet circuit is maintained by interposing non-magnetic materialbetween the pole faces or otherwise preventing the latter from coming incontact, the magnet is noisy, the chattering noise depending largelyon'the load placed on the magnet and being excessive where theload isheavy. Also the. non-magnetic material is subject to wear and eventuallypermits the pole faces to come together, and thus allows the residualmagnetism to assert itself. ln

vthe present invention these objections are overcome while at the sametime the efl cicncy and also the mechanical' strength of the magnet aremaintained.

l wish it to be understood that thepresent invention is not limited tothespecific structure herein disclosed, but comprehends all suchmodifications and structures as come within the terms and scope of theappended. claim.

What l claim is V in an electromagnet, the combination of oppositelydisposed members each comprisist df '1mm amv@ immun 'mu l en esl1molly imy an orme'd with projecting pole pieces, nameto this specication in thepresence of 1c said sleeves belng formed with spaces n the twosubscribing Witnesses. body of the ring between the pole pieces and'breaking the continuity of the magnetic path WILLIAM D' LUTZ' betweenadjacent pole pieces, said spaces Witnesses:

eng arranged to alternate n the said W. H. BRADY,

members. E. L. ANSTELL..

Copies of this patent may be obtained for ive cents each, by addressingthe Commissioner of Patents,

Wanhlngen, E). 0.

